University of California Berkeley scientists say they have found a way to advance on-chip inductor technology, triggering a new generation of miniature RF electronics and wireless communications systems.
The UC research delved into recent developments in nanomaterial synthesis of nanomagnets. Liwei Lin, a professor of mechanical engineering at UC Berkeley, told us the researchers found that using magnetic nanoparticles with a coating of insulators shrinks the size and improves the performance of high-frequency on-chip inductors. "They provide good magnetic permeability with high cutoff frequency while reducing the eddy current losses at high-frequency operations."
Engineers have had problems trying to reduce the size of on-chip inductors while maintaining optimum levels of inductance and performance. Difficulties stem from limitations set by "fundamental sciences and constraints set by engineering practice," Lin said.
On-chip inductor technology hasn't progressed the same way as transistor technology, which has followed Moore's Law over the past 40 years. Inductors -- technically passive elements in circuitry -- fall into the "More Than Moore" domain, in which devices integrate nondigital functions such as RF and MEMS that do not scale to Moore's Law.
When on-chip inductors are constructed, large areas are required, because they need a certain length, number of turns, thickness, and space between metal traces to achieve adequate levels of inductance and performance. However, the large area requirements produce inductance losses because of the parasitic effects between the spiral coil and the semiconductor substrate.
As a result, miniaturization will require the addition of magnetic materials, but they have their own technical limitations, "such as processing schemes, compatibility with standard processes, and material stabilities," Lin said. "Magnetic materials have fundamental limits on their permeability and frequency responses."
The new inductor fabrication technology, which uses insulated nano-composite magnetic materials as the filling material to reduce the size of the on-chip inductors, enhances inductance by up to 80%, resulting in at least 50% shrinkage in the on-chip inductor. It also has the potential to extend the operational frequency range from the GHz range to the 10-GHz range, Lin said.
He expects these advancements to be applied to the chip manufacturing process in 3-5 years.
The UC Berkeley research has been sponsored by Semiconductor Research Corp., the university research consortium for semiconductors and related technologies in Research Triangle Park, N.C.